Door actuating apparatus



phn ZL L. H' @RQSS DOOR ACTUATING APPRATUS 2 Sheets-Sham, l

Filed July l2, 1933 AFTER 219 w36 L. H. @Rcss QB DOOR AC TUT NGAPPARATUS' Filed July l2, 1933 2 Shee'bs-Shee 2 ,7g ma 5 /70 74 aNvENToREO /L/f @R055 Patented Apr. 21, 1936 UNITED STATES PATENT oFFlcE DOORACTUATNG APPARATUS Leo H. Gross, Bartelso, Ill.

Application July 12, 1933, Serial No. 680,021

14 Claims.

This invention relates to improvements in electric switching apparatus,and particularly to a power switch and switch-operating assembly for usein connection with power operators for the doors of garages and likestructure in which it may be desired to effect door movement by remotecontrol means. This invention constitutes a continuation, in part, of mycopending application, Serial No. 600,148, filed March 21, 1932.

An object of the present invention is attained in an improved andsimplified motor-switching device combining the functions of alimit-switch and a reversing switch for an electric door operator, withthe function of an overload-release switch, operable in any position ofthe doors to open the motor circuit in response to abnormal loadconditions arising from any cause.

Yet another object of the invention is attained in an improved motorswitch, serving the purposes of the object first above mentioned, whichswitch is of such type that it may be built into the motor frame.

Among the additional objects of the invention may be mentioned animproved inbuilt motor switch, susceptible of use with an electric motordirectly connected to its driven apparatus as through the use of a wormand worm gearing, the switch being of such a nature as to operateresponsively to axial movement of a motor shaft coordinately withoverload conditions in a transmission including worm gearing.

The foregoing and other objects will more fully appear from thefollowing description, considered in connection with the appendeddrawings of a presently preferred executional embodiment of theinvention. In the drawings:

Fig.V 1 is a vertical sectional elevation of a power door-operat0rembodying improvements according to the present invention; Fig. 2 is afragmentary horizontal sectional elevation of a switch structure such asappears in Fig. l, and illustrating on an enlarged scale, certainelements of the switch; Fig. 3 is an elevation of a movable switchplate, serving to carry some of the movable switch contacts of thestructure of Fig. 2; Fig. 4 is an alternate form of switch of a typewhich may be disposed entirely within a motor frame of usual design;Fig. 5 is an elevation illustrating a toggle mounting of the movableswitch plate of Fig. 4, Fig. 5 being viewed at a right angle to theplane o'f Fig. 4; Fig. 6 is a sectional elevation of an adjustmentemployed in connection with the toggle linkage of Figs. 4 and 5, andFig. 7 is a circuit diagram illustrating a simplified wiring arrangementof a power operator such as shown by Fig. 1, and the several switchesutilized in the assembly and including a limit and overload switch ofthe type illustrated by Fig. 4, for example.

Considering now, as exemplifying an application of the switching meanshereinafter claimed, a power operator unit as arranged for windingpaired door actuating cables, there is shown by Fig. 1 a frame structureconsisting of superposed decks or plates, such as 5| at the bottom, 52as an intermediate member, and 53 at the top. These decks or plates aresuitably assembled in spaced relation as by bolts 54 and spacer tubes55. These bolts or the tubes are preferably utilized to receive injournalling relation, pulleys 38 and 39.

A winding member or reel 56, which is in the nature of a hollow drum, isengaged in wrapped or wound relation by the cables 36, the bightportions of which are secured to the drum or reel 56 as by clamps orscrews.

tuated from a vertical shaft 51 projecting upwardly from the reel, andsecured to a worm gear 58 (Fig. l), engaged by a worm 59 secured to ashaft 60 of a motor, the frame of which is located generally at 6|, andprovi-ded with end bells or bearing arms 62 and 63. The end bell E2 isprovided with an extension or housing portion 64, serving as a journalfor the shaft 60, and also serving as a housing for the reception ofgrease or other lubricant packed about the worm 59 and worm gear 58.

The motor 6| is of reversible type and includes a stator 65 and a rotor66.

Carried preferably by the motor frame, say the end bell 63, is a motorswitch assembly hereinafter described in detail, it being presentlysufcient to indicate that this switch is in the motor circuit, and isoperated by -axial movement of the shaft 60 in response to overloadconditions imparted to the worm 59 and Worm gear 58, which condition,due to the abnormal thrust of the worm, serves to effect a movement ofthe shaft 60 in one direction or the other, along its axis.

In order to permit of a substantial axial of the sleeve or tube 6l.

The axial length oi!- The drum is acu the slot is such that as the shaft60 is axially moved in either direction, the pin 68 may traverse theslot endwise Without axially displacing the rotor 66. The pin and slotconnection also provides a lost-motion driving connection between therotor 66 and the shaft 60, since, when the motor circuit is closed, therotor 66 may revolve through substantially a complete revolution beforepicking up the load of the shaft 60 and related parts, and thus willfully overcome the friction at rest of the motor before being subjectedto the load of the doors and transmission. Since successive periods ofmotor operation will normally take place in opposite directions ofrotation, it will appear that the pin 68 will abut first one, and thenthe other face of the abutment formed by the cut away portion of thesleeve.

It will have been observed that my preference, according to Fig. 1, isto support the motor 6| on the deck 52, to which it is anchored as bymeans of the usual hold down bolts, the spacing between decks 52 and 53being such that the latter deck underlies the housing 64 as theimmediate support for this overhung portion of the structure.

Tol illustrate a useful adaptation of the subject matter herein claimed,there is illustrated a typical circuit arrangement in Fig. '7, in whichit is preferred that the motor heretofore designated at 6|, be of somestandard reversible type. Assuming by way of example, the motor to be ofalternating current type, a fractional horsepower, repulsion-inductionmotor is preferred. It is understood that in this type f motor, thedirection of initial current input will determine the direction ofrunning rotation. The motor is shown as provided with four leads 90, 9|,92, and 93, connected respectively to contacts 90A, 9|A, 92A, and 93A,the latter forming, with contacts 9,4 and 95, what may here be referredto as a double pole, double throw reversing switch, the preferredphysical embodiment of which is hereinafter described. It will appearthat, by connecting the terminal 90A to 94, and the terminal 93A to 95,the initial direction of current input is 0pposite that prevailing whenthe terminals 90A and .93A are connected respectively to the terminals9|A and 92A.

II he feeder circuit for the system is indicated by the conductors 96and 91. The latter leg of the feeder circuit proceeds directly to theterminal 95, as shown. The lead 96 is, however, provided withV a switch98 which may be located at any convenient point, and which, when openedand locked against closing, may be utilized to prevent unauthorizedactuation of they doors by the p ower operator. The leg 96 of the feedercircuit is further provided with a switch identified with a movableswitch member 99, serving to bridge contacts |00 and |0|, this switch,as hereinafter appears, being utilized as a limit switch forde-energizing the motor at or near each limit of its operation.

- For completeness, the circuit of Fig. 7 is shown as including severallight fixtures, such as one shown at |02, controlled by switch |03; adriveway control station switch |04, a garage light 1| a house switch|08 and driveway switches |09 and I0.

Considering the structure of the reversing and limit switch assemblyidentified with Figs. 1 to 6, the switch assemblies of Figs. 1 and 2 areidentical as to structure, and may be identical with the structure ofFig. 4A except for a slightly differing arrangement of compressionsprings employed to enhance the snap action of the switch. In theassemblies of Figs. 1 and 2, a single spring ||5 serves this purpose,and in Fig. 4 a pair of springs 6 and ||1 operate respectively to opposeaxial movement of shaft 60 and to urge the movable switch members totheir opposite motor-reversing positions. The arrangement of Figs. 1 and2 is preferred in heavy duty units, while that of Fig. 4 is preferred,by reason of compactness, in the case of lighter domestic installations.Considering first the structure of Fig. 4, there is mounted within theend bell 63 of the motor, a bracket ||8 serving to carry an insulatingplate H9, projecting inw-ardly of which, in parallel relation, are fourconductor studs |20, |2|, |22, and |23 (see Fig. 5). These conductor andguide elements project inwardly of the motor and are provided at theirinner ends with a spacer plate |24 connected to the conductor rodsthrough insulating bushings |25, the plate |24 serving, as appears fromFig. l, to limit the movement of the rotor 66 of the motor 6|, in onedirection along the shaft 60. Slidably mounted on the four studs ||23,is a slidable frame or carriage consisting of a pair of plates |26 and|21, each provided with metal contacting bushings |28 which serveslidably to embrace the conductor studs |20-|23. Each of these bushingsincludes a strap portion extending inwardly, for contact purposes, fromthe conductor stud or guide with which it is associated. The two plates|26 and |21 are preferably formed of insulating material such as a rigidfiber, and are maintained in spaced parallel relation by tubularinsulating spacers |29, being also centrally bridged by a tubular member|30 surrounding that portion of the shaft 60.

Mounted for slidable movement between the plates |26 and |21, is aninsulating plate |35, centrally apertured as at |36 to receive throughthe aperture, the tubular element |30. The insulating plate carries onone face (Fig. 3) a pair of spaced parallel conductor strips |31 and|38, disposed vertically in the assembly, while on the opposite face ofthe plate are mounted a pair of similar horizontal conductor strips |39and |00. The strips 31| 40 constitute the movable elements of thereversing switch identified diagrammatically in Fig. '7. Disposed on oneface of the insulating plate |35 is an additional conducting strip shownat 99, and extending across and marginally beyond each side of theplate. The strip 99 (Fig. 3) constitutes the movable element connectingthe contacts |00 and |0| according to the diagram of Fig. 7. The strip99 serves normally when the motor is in operation, to bridge inwardlyextending contact portions |4| of a pair of spring contact fingers,which for convenience of reference to the diagram of Fig. 7 may bedesignated as |00 and |0|.

In case it is desired to control the energization of the light fixture1| within the garage or like structure, according to the position of thedoors and hence of the parts of the power operator, there isconveniently provided, say on the outer face of the plate |21, aconducting strip designated to correspond with Fig. '7 and strip |05.'Ihe strip |05 is adapted, when the switch elements are in their righthand position (Figs. Zand 4) bridgingly to engage a pair of springfingers or con. tacts |06 and |01. It will thus ,appear that, with themovable switch parts in one extreme of the range of movement, the switch|05-I 01 is closed and, whenever the switches 98 and |08 are closed,

the fixture 1| will be energized to provide interior illumination forthe building.

It will have appeared from Figs. 1, 2, 3, 4, and 5, that it is desirablefor the plate |35 to be moved with a snap action across the spacebetween the plates |26 and |21 of the slidable frame. This result isaccomplished through the provision of pivot studs or trunnions |45secured to opposite margins of the contact plate. These studs engageslotted openings |46 near the free ends of a U shaped member |41,pivoted at |48 to a stationary U frame |49, conveniently supported, asby riveting, to the bracket ||8. A depending toggle frame of U shapeindicated at |50 also pivotally engages the frame |49, and is centrallyapertured to receive one end of a thimble |5|. The thimble is internallythreaded to receive an adjustable T shaped element |52 (Fig. 6) a jambscrew |53 being utilized to retain the threaded element |52 in adjustedrelation within the thimble l5 The inner end of the thimble |5| isprovided with a collar |54 serving as an abutment for a toggle spring|55, the outer end of which abuts against the lower portion of the Uframe |50. The T shaped element i 52 has its head portion transverselyapertured as at |56 to receive a pivot pin secured through the arms of aU shaped yoke |51, this yoke being secured centrally to the lowerportion of the toggle bracket |41, the relation of these parts bestappearing in Figs. 4 and 5. It will appear that the parts |41 and |50,being connected through the spring |55, will tend, under the loading ofthe spring, to assume an angular relation as in Fig. 4; further that, asthe slidable frame |26|21 is moved to its opposite limit, the tendencywill be first to center the toggle, thence with a snap action due to theloading of spring |55, cause the parts |41 and |50 to assume an oppositeangular relation.

It will have appeared heretofore that actuation of the reversing andlimit switch assembly is effected through the axial movement of shaft60. This axial shaft movement is imparted to the slidable frame |26-|21,and hence to the plate |35, through the agency of a ball thrust bearingof special design embodying ball elements |60 operable in a shaft groove|6|, and within a race |62 carried by a two part collar |63 whichconveniently constitutes a part of the element |30. The collar |63 alsoserves as an abutment for one end of the spring ||1, the opposite end ofwhich is anchored by engagement with the bracket ||8. The spring I|6 islikewise engaged by a similar bearing assembly |63 at one end, and atits opposite end by the plate |24.

In the structure of Fig. 2, the slidable frame, the toggle arrangement,the frame-guiding conductor studs are all, or may be, identical withthese elements of Fig. 4. In Fig. 2, however, the spring l5, serving thepurpose of springs I6 and I |1 of Fig. 4, is mounted outwardly of themotor bearing arm on the shaft 60. As best appears in Fig. 1 the shaft60 is provided with an antifriction thrust bearing assembly consistingof an inner race |65 and an outer race |66, the former being secured tothe shaft as by a set screw and the latter being carried internally of acollar |61. The collar |61 is connected through paired distance rods |68pinned to the collar |61 and engaging, at their inner ends, the plate|21 of the slidable frame. This assembly is supported, and the rodsmaintained in spaced relation, through a plate |69 which is apertured toreceive slidably the distance pieces |68, and is in turn slidablymounted on fixed rods |10 carried by and secured to the end bell 63. Itwill appear from Fig. 1 that the rods |68 are slidably operable throughapertures |1| therefor, in the end bell, and that the rods |68 areshouldered as at |12 so as to abut a plate |13 which is slidable on therods |68 and forms an abutment for the inner end of spring I5. Theopposite end of spring H5 is engaged by a threaded nut or collar |14engaging an externally threaded bushing, for purposes of adjusting theloading of spring l5, the bushing being indicated at |15.

The operation of the springs ||6 and ||1, is selective, according to thearrangement of Fig. 4, the former serving to resist the movement of theslidable frame, and hence of the shaft 60, to the left, and the latteropposing the movement of the frame and shaft to the right. According tothe spring arrangement of Figs. l and 2, axial movement of shaft 66 tothe right, serves, through the thrust bearing, to move the collar |61 tothe right. This movement is transferred through rods |68, particularlythe shoulders |12 thereof, to the plate ll bearing against the left handend of spring l l5, the nut |14 and plate |69 being held againstmovement to the right by the heads of pins |10. Thus it is seen that thespring ||5 will be cornpressed and its loading serve to resist movementof the slidable frame, in this direction. When, however, the frame andshaft can overcome the spring loading, the movement of the frame will besuch as to move the contact carrier plate |35 a suffi-cient distance tothrow the toggle, when the strip 69 will clear parts 14| to open themotor circuit. The strips Mil- M0 are now positioned so thatreenergization of the motor will cause it to start in the oppositedirection.

When the tendency of the Worm and worm gear, due to resistance torotation of the worm gear, is to move shaft 66 to the left, it willappear that the collar |61 will act upon rods |68 and tend directly tomove the slidable switch frame to the left. The left hand end of thespring remains stationary because of the abutment of plate |13 againstthe end bell |63. The plate |69 is however free to slide on the rods |10to permit a compression of the spring to the left, as it appears in Fig.l. It thus appears that the spring |55 will serve to resist axialmovement of shaft 66 in either direction, and to augment the action ofthe toggle arrangement identied with the frame 50 and yoke |61.

The switch action of the parts of Fig. 4 is essentially the same as thatof the structure of Figs. 1 and 2. Upon movement of the slidable frameto the right, the spring ||1 is compressed between the structure |63,and the plate ||8. Upon movement of the switch frame to the left, thespring i6 is compressed between the bearing |63, the adjacent plate 26,and the plate |24.

It thus appears that, irrespective of the spring arrangement employedwhen the plate |35 is in one position between the plates |26 and |21,the vertical conductor strips |31 and |38 will directly connect, throughone of such strips, the conductor guide studs |25 and |22, and throughthe other of such strips, the studs |2| and |23. When the plate |35 isin its opposite extreme position and engaging the other of the platestt-|21, one of the horizontal strips |39 will serve to connect the studs|20 and I2 while the other, 40, will serve to connect the studs |22 andi, thus providing selectively either the normal or crossed relation ofconductors to care for the reversal of current input according to thedlagram of Fig. 7. In order to correlate the switch structure with thediagram of Fig. 7, screw terminals are shown in Figs. 2, 4, and 5, asbearing the numerals corresponding to those of Fig. 7.

From the foregoing it will appear that the plate |35 and contactscarried thereby together with the conductor studs H20-|23 constitute themotor-reversing switch while the elements 99, |00, and |0| of thisstructure constitute the limit switch for the motor. It will furtherappear that the slidable switch frame I 2li- |21 is moved from oneextreme to the other of its range, through the axial movement inopposite directions of the shaft iii) under the iniiuence of the wormand Worm gear, due either to attainment of end positions of the drivenapparatus, or to overload condition. The augmented thrust of shaft 60thus serves to shut off the motor through the action of the strip S9 andcontact fingers |00 and IBI, at the same time disposing the reverseswitch elements in such position that when the motor is reenergized, thepower operator is started in the opposite direction.

It will be observed from Fig. 2 that, when the switch parts are in theirleft hand position, with the motor at rest, the strip 99 fails to bridgethe contacts |00 and |0|. When, however, the motor is started, as forexample by closing one of the driveway switches or the switch |08, theswitch 98 being closed, starting current is shunted around the switch99, |00, I0 so as to initiate operation of the unit. As soon as this isdone, the working torque of the motor and the worm is suflicient tomove, axially, the motor shaft, the slidable switch frame, and hence theplate, to a position in which strip 99 bridges the contacts |00-|0|. Theinturned ends |4| of the contacts |00-|0| are likewise cleared by thestrip 99, as the plate |35 and frame S26- I 2'! are moved to their righthand positio-n. Upon restarting the motor, which will then operate inthe opposite direction, the working torque of the motor and worm issufficient to restore the strip 99 to a bridging relation with the partslll of the contacts |00-|0|.

From the circuit of Fig. '7, switch |04 being closed, it will appearthat closing either of switches |09 and ||0 will normally close theshunt leg of the lead .S4- 96 and will thus serve initially to energizethe power operator motor and to maintain the current input until thecircuit is closed through the switch 99, |00, |0|.

It will further appear that the several items of structure heretoforedescribed constitute marked improvements in the production and operationof devices of the present order; that the motor control and switchingarrangement is substantially simplified over those heretofore offered tothe trade, and rendered more reliable in operation, in fulfillment ofthe several objects above set forth.

While I have described the invention by making specific reference tocertain definite, preferred embodiments thereof, it is to be understoodthat the details of the disclosure are to be understood as exemplifyingthe invention, rather than a limiting sense, since a number of changesmay be made in the parts, their combinations and assembly, withoutdeparting from the full scope of the invention defined by the appendedclaims.

I claim:

1. A switch mechanism including, in combination with an axially movableshaft, a Contact support adapted to be shifted responsively to axialmovement of shaft, a contact carrier operable along the shaft, contactson the support, and contacts on the carrier adapted selectively toengage those on the support, a spring and lever mechanism for actuationof said carrier, and a connection from the support to said shaft, formoving the support responsively to axial movement of the shaft.

2. A combined reversing and limit switch assembly for an electric dooroperator motor, including an axially movable shaft, a plurality'ofmovable contacts for the reversing switch, reversing switch contactsadapted to be engaged by said movable contacts, a plurality of movablecontacts for the limit switch, other contacts adapted to be engaged bythe last said contacts, a member constituting a carrier common to themovable contacts of both switches, and means for causing a movement ofsaid carrier responsively to axial movement of said shaft.

3. A switch mechanism including, in combination with a rotatable andaxially movable shaft, a plurality of stationary contacts spaced in thedirection of the shaft axis, a contact carrier, contacts on the carrieradapted selectively to engage the stationary contacts, means connectingthe carrier for movement respo-nsively to axial movement of the shaft,means for imparting an axial movement to the shaft responsively to apredetermined shaft torque, and spring means tending selectively to urgethe carrier toward and away from the stationary contacts.

4. In a switch mechanism, in combination with an axially movable switchactuating shaft, a pair of spaced plates, contacts carried on opposedadjacent faces of said plates, a carrier operable between the plates,contacts on the carrier, means for moving the said plates responsive-1;/ to axial movement of the shaft, elements for slidably supportingsaid plates, and means tending to bias the carrier toward the plates,one at a time, responsively to axial movement ofthe shaft.

5. A switch mechanism including, in combination with an axially movableshaft, a plurality of conductors disposed parallel to said shaft, aframe slidably carried by said conductors contacts carried by said frameand connected to said conductors, a contact carrier movable along saidshaft, and movable with respect to said frame,

contacts on the carrier adapted to engage those if on the frame, meansconnecting the frame and shaft for movement of the frame responsively toaxial movement of the shaft, and spring means tending selectively tourge the said carrier into and out of engagement with the frame.

6. A switch mechanism including, in combination with an axially movableshaft, a plurality of conductors disposed parallel to said shaft, aframe slidably carried by said conductors, contacts carried by saidframe and connected to said conductors, a contact carrying plate movablealong said shaft, toward and away from said frame, contacts on the plateadapted to engage those o-n the frame, means connecting the frame andshaft to cause a movement of the frame responsively to axial movement ofthe shaft, a spring tending selectively to urge the carrier into and outof engagement with the frame, responsively to movement of the frame, andspring means tending to oppose axial movement of the shaft.

7. A combined reversing and limit switch for an electric motor,including an axially movable shaft, a frame including a pair of spacedinsulating plates assembled in spaced relation, a connection from theshaft to the frame whereby the frame is adapted to be shiftedresponsively to the axial movement of the shaft, a contact carrieroperable between the plates of the frame, contacts on the inner surfacesof the plates and the companion contacts on the opposite surfaces of thecarrier, a spring and a lever cooperating to provide a snap movement ofthe carrier from each plate to the other thereof as the shaft is axiallymoved, spring means opposing the axial movement of the shaft, aplurality of stationary contacts disposed along the path of the movementof the frame and carrier, and a conducting member on the carrier adaptedto bridge said stationary contacts.

8. A switch mechanism including, in combination with an axially movableshaft, a plurality of stationary contacts, supporting means therefor, amovable frame having contacts slidably engageable with said stationarycontacts, a support on which said frame is slidably mounted, a contactcarrier movable along the shaft, and with and within said movable frame,means connecting the movable frame for movement responsively to axialmovement of the shaft, and spring means for actuation of the carrier inthe frame, and toward and away from the stationary contacts.

9. A combined current reversing and circuit opening and closing switchand cooperating means therefor, for use in a supply circuit ofelectrically driven apparatus and including in combination with anaxially movable and rotatable shaft, a spring structure compressible ineither direction, and connected to said movable shaft, a movable switchmember and contacts thereon for opening the associated circuit when thespring structure is held compressed in either direction, means operableby `axial pressure on the said shaft in each direction, for' opening theswitch, said means being further adapted for automatically closing theassociated circuit when said pressure is released.

10. A combined reversing and circuit controlling switch for a supplycircuit such as that of an electric motor, the switch including arotatable shaft element, an axially movable connection thereto, aplurality of stationary contacts, a support therefor, a contact frameand contacts thereon, slidably carried by the said stationary contacts,a contact carrier and contacts thereon, movable with and within saidcontact frame and along the shaft, a spring and lever mechanism havingthrough the carrier an operative connection to the frame serving toactuate said contact carrier in said contact frame, and a double actingspring device connecting said contact frame with said movable connectionto the shaft.

11. A switch and switch-operating mechanism for controlling an electricsupply circuit and including an axially movable and rotatable shaft, amovable contact member, contacts in the supply circuit and coactingtherewith, means fo-r shifting the movable contact member responsivelyto axial movement of the shaft, means for imparting a snap movement tothe movable contact member as it approaches its limits of movement, andmeans responsive to shaft torque, for actuating the movable contactmember.

12. In a switch and switch-operating assembly, in combination with anaxially movable and rotatable shaft, a movable contact member, contactsthereon, other contacts selectively engageable thereby, means forshifting the movable contact member responsively to axial movement ofthe shaft, a spring, a toggle connection between the spring and themovable contact member for effecting a snap action of the member intocircuit changing position, and means responsive to changes in shafttorque for axially displacing the shaft and actuating the movablecontact member.

13. In a switch and switch-operating assembly, in combination with anaxially movable and rotatable shaft, a movable contact member, contactsthereon, other contacts coacting therewith and mounted separatelytherefrom, means for shifting the movable contact member between circuitchanging positions responsively to axial movement of the shaft, a springyieldably opposing axial movement of the shaft, means for adjusting theloading of the spring, yieldable means for imparting a snap movement tothe movable contact member as it approaches a circuit changing position,and means responsive to shaft torque for axially moving the shaft, andthereby the movable contact member.

14. In a switch and switch-operating assembly of a type for actuationby, and in combination with an axially movable and reversibly rotatableshaft section, a movable switch member and contacts coacting therewith,means for shifting the switch member responsively to axial movement ofthe shaft, a spring device opposing axial shaft movement in eachdirection, means for adjusting the loading of the spring device, aspring and toggle linkage actuated by the movable switch member andarranged to impart a snap action thereto, and means responsive to apredetermined operating load on the shaft, in each direction ofoperation, for effecting an axial movement of the shaft wherebyeffectively to actuate the movable switch member.

LEO H. GROSS.

